Question

A 5.0-liter gas tank holds 1.4 moles of helium (He) and 0.70 moles of oxygen (O₂), at a temperature of 260 K.

The atomic masses of helium and oxygen are 4.0 g/mol and 16.0 g/mol, respectively.

The total random translational kinetic energy of the gas in the tank is closest to

Answer 1

K for one molecule:

$K = \frac{3}{2}kT \\ = \frac{3}{2}(1.38 \times 10^{-23}\;J/K) (260\;K) \\ = 5.38 \times 10^{-21} \;J$

All molecules:

$(1.4 \times 6.023 \times 10^{23} + 0.7 \times 6.023 \times 10^{23}) \times 2.38 \times 10^{-21} \;J \\ = 6.8 \;kJ$